1. Field of the Invention
This invention relates to a pull string mechanism in a pull string type sound reproducing device wherein the energy spent for pulling a string connected to a constant torque spring is initially stored in a constant torque spring, and thereafter the stored energy is utilized to reproduce the recorded sounds.
2. Description of the Prior Art
As prior art, there is an invention disclosed in U.S. Pat. No. 4,004,815 corresponding to Japanese Utility Model Publication No. Sho 58(1983)-28408 as, generally, shown by FIGS. 5 and 6 of the attached drawings.
This device comprises an upstanding center shaft 2 disposed in a casing 1. A rotary member 3 disposed around the shaft 2 is resiliently supported and is axially moveable along the shaft by a stylus force spring 4. Alongside the rotary member 3 a constant torque spring 5 is disposed so as to energize the rotary member 3 in the direction of rotation. The shaft, also, carries thereon a turntable 6 and a bobbin 7 which are rotatable integrally with the rotary member 3.
The device, also, includes, a pull string 8, one end of which is attached to the bobbin 7, and the other end of which is extended outside the casing through a pull-out hole or opening 16 positioned below the level of the turn table 6, and a spring 9 for sustaining the string so that the string 8 does not contact the turntable 6 during the time when the string 8 is not being pulled and not in a stretched state.
The device is further equipped with a rotatable tone arm 14 which abuts the cone head 11 of the speaker cone 10 fixed to the casing 1 and is supported in such a manner that a sound reproducing stylus 12 can engage the record disc 13 under the resilient force imparted by the stylus force spring 4 of the turn table 6. A return spring 15 urges the tone arm 14 toward the starting point of sound reproduction. The device, also, includes a governor 18 which regulates the rotating speed of the record disc 13.
The device operates in the following manner:
The constant torque spring 5 is wound up around the rotary member 3. Then the rotary member 3 is ready for rotation.
When the rotary member 3 rotates, the turntable 6 and the record disc 13, also, rotate together. When the rotating speed of these members is too fast, the speed of rotation is regulated by the governor 18.
During rotation, the tone arm 14 travels toward the center of the record disc 13 accompanying the reproduction stylus 12. The motion of the stylus 12 transmits the sounds to the cone head 11 so as to be mechanically amplified by the speaker cone 10, since the stylus is kept in contact with the record disc 13 while the tone arm is kept in contact with the cone head.
When the constant torque spring 5 completely returns to its original un-loaded state, the pull string 8 is pulled again to energize the constant torque spring 5 for the next playing. The pull string 8, in the pulling motion, however, is inevitably stretched slantedly downwardly toward a level lower than the turntable 6 and urges the record disc 13 to move downward away from the tip end of the reproduction stylus 12. Since the tone arm 14, which is integral with the reproduction stylus 12, has been moved to the end point of sound reproduction by virtue of the friction between the reproduction stylus 12 and the record disc 13, absence of friction between the two members, as stated above, will allow the tone arm 14 and the stylus to move to the starting point of sound reproduction. Thus the device is now ready for next playing.
There is other prior art as disclosed by Japanese examined Patent Publication No. Sho 58(1983)-46778 and U.S. Patent Application Ser. No. 428,000 (abandoned) corresponding to Japanese unexamined Patent Publication No. Sho 59(1984)-19275 and U.S. Pat. No. 4,547,873.
In order to repeat the above operation in those prior art devices, the pull string must be securely and tightly wound around the bobbin disposed on the record disc, when the last reproduction has been completed. Otherwise, the pull string will run off outside the bobbin so that it either makes it difficult to sufficiently energize the constant torque spring for the next playing or the string may wind itself around some other undesired portions of the device so as to be impossible to pull out the string, or sometimes, even to energize the constant torque spring.
Such problems may be solved by widening the upper flange of the bobbin. However, a widened flange bobbin would abut the tone arm when the tone arm arrives at the portion somewhat adjacent to the end point of sound reproduction. This makes it necessary to enlarge the diameter of the record disc in order to ensure the length of time of sound reproduction is the same as that already accomplished by the prior art device. However such remedial ways make it difficult to minimize the overall size of such devices.